Optical means for increasing rear vision



350.443 5;; OGHFCH mom OR @123 "E92 Nov. 1, 1938. E. w. SCHUMACHER 2, 6

OPTICAL MEANS FOR INCREASING REAR VISION I Filed Feb. 10, 1936 2 Shuts-Shoot 1 T1 6 2 I X 2 6 4 7 Search Room Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE OPTICAL MEANS FOR INCREASING REAR .VISION This invention relates to improvements in optical systems for increasing rear vision in vehicles and other devices requiring such increased vision.

Referring to the drawings, wherein like reference characters denote like parts throughout, Fig.

I shows in outline the transverse elevation of an automobile. The eye of the driver is assumed to be located at I.

A principal object of the invention is to pro- The eye I is aligned with a mir- 5 vide optical means to increase rear vision in 9. 2 S0 angled as to reflect t0 the ye I e image vehicle or other object requiring such vision. of the rear window 3 and Objects See e- Another object of the invention is to provide throughsimple, eflicient, and inexpensive means for ob- Ordinarily. With a Plane glass dow at 1O taining rear vision in vehicular objects and other objects fairly Close t the mobile in t e devices requiring such vision. rear cannot be seen in the mirror 2 by the eye 1.

Other objects and advantages of th inv n- In the device of the invention mirror means 2 tion will become apparent from the following de- Optically equivalent o a co ave reflector is 10- scription taken in connection with the accom- Gated in front of the ye and S0 a ed as to panying drawings. It will be apparent th t image the window 3 and the plane glass window 3 15 changes may be made in the details of cons replaced y a ne a v l ns w h ne ative struction and arrangement of parts without delens W ll Widen the fi l Of V w hr u h the winparting from the spirit of the accompanying dow 3 as imaged on the mirror 2, as hereinafter claims; hence, it is not desired t li it th i described, and thus enable the driver to see on vention to the exact details, and arrangements the m rr Objects n h r r close 11p to the rear shown and described, as the preferred forms only of the l. y w h he m y be guided wh n are given by way ofil1ustration backing up. The concave reflector also widens Referring to the drawings: the field of vision as will be hereinafter de- Fig. I is a diagrammatic sectional elevation of scribedthe invention as applied to an automobile; f ring to Fig. w r e f n ion of 25 Fig. 11 is a diagrammatic plan view illustrating the negative lens 4 is illustrated, the eye is asthe function of the rear negative lens portion of sumed to be located at and Visien is ected the device embodying the invention; at the mirror 2, angled to image the negative Fig. III is a diagrammatic plan view of the lens 4.

modified form of rear negative lens and illus- The image of he eye f rme y h lens 4 30 trating its function; will be located at 5. The focus of lens 4 is at 6. Fig. IV is a plan view of another modified form The point 7 is the equivalent Point Of the ma e of rear negative lens; of the eye by the mirror 2, or the effective point Fig. V is an end view of Fi IV, of the eye I. The line 8 represents an extreme Fig. VI is a plan view 01' a, i d w and m; line of vision at the edge of the lens 4. The line 35 rear negative lens used in a modified form of the 9 from the Point 5 r h the P nt Where the device; line 8 intersects the lens 4 on the rear surface Fig, VII i a d i w of Fig VI; represents the increased angle of vision through Fig. VIII is a diagrammatic plan view of anthe lens 4 indicated by the angle Ill.

other part of the invention looking in a down- The opt al fo u a nvolved here is 40 ward direction as if the top of the vehicle had 1 1 1 been removed;

Fig. IX is a view similar to Fig. VIII showing the device of Fig. II combined with that of Fig. Where W denotes the distance of the eye from VIII; the lens 4, V denotes the distance of the image 45 Fig. X is a view generally similar to Fig. VIII of the eye from the lens 4, and denotes the of a further modified form of reflective means. focus of the lens 4.

It is well known that while most automobiles Let us assume W equals 80 and equals minus have rear windows the vision through same is 40; then we have so restricted in backing up that the driver can- 1 1 1 80 50 not see objects close up in his path while backor, V equals 3 ing. It is, therefore, a principal object of this invention to so optically increase the field of or -27 inches (about). vision that such objects may be seen and the In Fig. III, which is a modification, the lens operation of backing facilitated and made safe. 4 is replaced by a split negative lens, having the 55 parts II and I2 spaced apart and held on the rear window I3. In this modification the increased vision is represented by the angle I4, the optical properties and formula being otherwise the same as for Fig. II. In this modification the objects will be seen through the window I3 between the edges of the lens parts II and I2 as of normal size, and through the lens parts as of reduced size.

The whole window 3 may be made of a single negative lens 4, as shown in Fig. II, or part negative lenses may be secured on the rear window I3, as shown in Fig. III. The parts II and I2 may be cemented on the window I3 by Canada balsam or other adhesive, or they may be otherwise held in place by any suitable mounting, either on the window I3 or in line therewith, as desired.

The lenses 4, II, and I2 may be either spherical or cylindrical, as desired. The lens may be designed only to direct the image downward, as shown in Figs. IV and V, or it may be made to direct the image sidewise at either end, as desired. This may be accomplished by making the lens in the form of a prism and by positioning the base of the prism in the direction of desired increased vision. The same thing may be done with the lenses II and I2, as shown in Figs. VI and VII, that is, the lens sections may be arranged top and bottom as shown, or at either side, as desired.

Instead of negative lenses at the rear window, prisms may be used to direct the image in any direction required or double mirrors may be substituted for the same purpose.

In Fig. VIII the characteristics and function of one of the mirror means of the invention is shown. The mirror means in this instance is illustrated as being formed of a plurality of spaced mirror sections I5, I5 or I5, and in Fig. X as being a concave cylindrical mirror 21. The concave mirror bfsiaced sections I5, I5 or I5" may be used instead of the single plane mirror 2 illustrated in Fig. I. This cylindrical mirror may be a section of a cylinder, a true cylinder, or a plurality of plane mirrors approximating the position of and tangent to the curvature of the curved mirror. These mirrors are so located relative to the eye I6 of the observer, and to the window I! of the vehicle, as to increase the angle of vision through said window by the amounts indicated at l8 and I9. The increase in the angle of vision may be confined to only the opposed sides of the vehicle, as indicated at I8 and I9, but may also be in an upwardly and downwardly direction. The window I! in this instance is of the prior art plane plate glass type.

The mirrors or sections of mirrors I5, I5 or I5" are located as shown diagrammatically in Figs. VIII and X, at such positions as to obtain the greatest possible increase in angle of vision through the rear window II.

It will be noted that the section l5" or one portion of the concaved mirror 21", as shown in Fig. X, is positioned to the left of the body portion of the vehicle and to the left of the observer, who may be seated in the front of the vehicle, and that the section I5 or another portion of the concaved mirror 21" is positioned to the right of the body portion and to the right of the observer. The reflecting means I5 or corresponding portion of the concaved mirror 21" will, therefore, provide increased vision at the left of the body portion, and the reflecting means I5" or corresponding portion of the concaved mirror 21f will provide increased vision at the right of the body portion, the angles of vision crossing each other between the front and rear of the body portion, and the point of intersection being substantially the effective position of the eye of the observer. This point of intersection is illustrated at 22 in Figs. VIII and X.

In these diagrammatic illustrations the lines 20 indicate the prior art angle of vision as obtained by a mirror similar to that illustrated at 2 in Fig. I, and located as at 2| in Fig. VIII.

The use of a concave mirror or plurality of sec tions I5, I5 or I5", produces an effect similar to locating the eye of the observer somewhere between the rear window I I and the front of the car at a position substantially approximating that indicated at 22 in Fig. X. Optically this places the eye of the observer nearer the rear window I'I, whereby the view through the rear window is correspondingly increased by the amounts indicated at I8 and I9.

In Fig. IX there is shown the combination of the mirrors l5, I5, etc., of Fig VIII, and the concaved window 4 of Fi II. This increases the angle of vision by he amounts indicated at 23 and 24, one increase in angle being brought about by the principle set forth in connection with Fig. VIII, and the other by the principle set forth in connection with Fig. II. The combining of these two principles, as set forth in Fig. IX, will thereby greately increase the angle of vision through the rear window II.

It is apparent that although Fix. IX only illustrates the use of the window 4, windows of the type shown in Figs. V and VII may also be used, in combination with the arrangement shown in Fig. VIII, to bring about a further increase in the angle of vision.

It is apparent, therefore, that if only an increase in vision of the amount illustrated at I8 or IS in Fig. VIII, is desired, the principles illustrated in said figures might be used; but if it is desired to obtain a further increase in the angle of vision, a combination of the principles illustrated in Fig. II and Fig. VIII may be used. This combination, and the consequent increase in the angle of vision, is shown diagrammatically in Fig. IX.

The image of the eye, as formed by the lens 4 in the arrangement shown in Fig. IX, will be effectively located at 5. The focus of the lens 4 will be approximately at the point 5. It will be noted that the points 5 and 5 are illustrated as lying on a line 25, which line in this instance designates the angle of reflection of the mirror I5. By eifectively locating the eye of the observer at the point 5 on line 25, an increase in the angle of the field of vision through the window 4 by the amount illustrated at 24 will be obtained.

While this invention is particularly applicable to automobiles, it is very evident that it may be used in many other devices where similar conditions obtain, and the object is generally the same.

From the foregoing it will be seen that I have provided simple, efficient, and inexpensive means for obtaining all the objects and advantages of the invention.

Having described my invention, I claim:

1. In a device of the character described for use in combination with a vehicle body having a rear window, reflective means optically equivalent to a concaved cylinder reflector positioned in the front of the body and so disposed relative to said body and rear window as to reflect light received through said rear window to a. point of observation within and near the front of said body, said reflective means having spaced reflective points all lying on the line of a section of a circle having its concaved side toward the rear window with the radius of curvature of said circle greater than the distance of said observation point from said reflective means, the said reflective means being so disposed relative to each other and to said body and rear window as to receive light rays passing through said rear window at angles which intersect each other at a point intermediate said rear window and front of the vehicle and reflect the said light rays to said point of observation.

2. In a device of the character described for use in combination with a vehicle body having a rear window, concaved reflective means positioned in the front of the body and so disposed relative to said vehicle body and rear window as to reflect light received through said rear window to a point of observation within the body, the concaved side of said reflective means being directed toward the rear window and the radius of curvature of said concaved side being greater than the distance of the observation point from said reflective means, said reflective means having reflective points so disposed relative to each other and to said body and window as to receive Search Roorr light rays passing through said rear window at angles which intersect each other at a point intermediate said rear window and front of the vehicle and reflect the said light rays to said point of observation. 5 3. In a device of the character described for use in combination with a vehicle body having a rear window, concaved reflective means positioned in the front of the body and so disposed relative to said vehicle body and rear window as 0 to reflect light received through said rear window to a point of observation within the body, the concaved side of said reflective means being directed toward the rear window and the ,radius of curvature of said concaved side being greater 15 than the distance of the observation point from said reflective means, said reflective means having reflective points so disposed relative to each other and to said body and window as to receive light rays passing through said rear window at 20 angles which intersect each other at a point intermediate said rear window and front of the vehicle and reflect the said light rays to sd point of observat ammaryavmg optical characteristics 25 l which will further widen the angle of vision @ugh the window as imaged on the regeriig eans. W

-- "ETL1VIER WELDON SCHUMACHER. 

